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If you’re like most of the exercising public, you up-sell your response so that it represents the very best of your exercise habits and ignore those days when you struggle to work up even the smallest of sweats.

That same tendency to gloss over the facts occurs when recalling food consumption, with most people conveniently forgetting the nibbles before dinner and the second helping at lunch.

Self-reporting bias is well-known among researchers who spend their careers polling Jill and Joe Public about their eating and exercise habits. So prevalent is the tendency to present the best of ourselves, some studies claim that from half to three-quarters of those queried overreport their exercise frequency and/or under-report the amount food they eat. But those aren’t the only instances in which the average exerciser paints too positive a picture of health habits. We also have a tendency to overestimate how hard we exercise.

A Canadian study out of York University asked 129 exercisers between the ages of 18 and 64 to walk or jog on the treadmill at a speed they felt corresponded with light, moderate and vigorous intensity. They maintained the required intensity for three minutes, all the while wearing a heart-rate monitor that registered their actual effort. Individuals were then asked to walk at the minimum pace they believed necessary to provide health benefits.

Turns out most of the group were able to correctly estimate light effort, but underestimated the intensity necessary to boost their exercise into the moderate and vigorous zone.

Also interesting was the discovery that when asked by the researchers to walk at a speed vigorous enough to benefit health, only 24 per cent picked up the pace enough to take their walk into the brisk zone. The others strolled along too slowly to qualify their walk as a workout.

That there remains confusion concerning what moderate and vigorous intensity feels like isn’t all that surprising. The ritual of manually checking heart rate to determine exercise effort disappeared sometime in the late 1980s. Back then, instructors cued everyone in fitness classes to take their pulse at least twice during a 60-minute workout, a practice that was eventually replaced with something called perceived exertion, which suggests that you are your best judge of how hard you’re exercising.

So instead of urging exercisers to work out in their training zone (between 70-85 per cent of their maximum heart rate as determined by subtracting your age from 220), simpler tools like the talk test — if you can talk but not sing during a workout, it’s considered moderate intensity exercise — were used to keep people exercising at a pace they could sustain.

About the same time as heart-rate monitoring fell out of favour, the definition of exercise broadened. House and yard work was considered light to moderate exercise and the message that any physical activity was good for you was born. Yet this idea that exercise didn’t need to be intense muddied the line between plain old everyday movement and the kind of exercise that makes you short of breath and puts a shine on your forehead.

Part of this change of pace was related to new research suggesting that health benefits were attainable from far less vigorous physical activity than previously thought. And that something as easy as a brisk walk could be good for your health. The focus of exercise shifted from intensity to quantity, which has left most exercisers with a poor understanding of what a light, moderate and vigorous workout feels like.

Why does that matter? Well, with the latest guidelines recommending 150 minutes of moderate exercise or 75 minutes of vigorous exercise a week, it helps to know whether you’re working up enough of a sweat to reap the rewards of your efforts.

How hard is vigorous? According to the York study, a light effort is characterized by a heart rate of 50-63 per cent of your maximum heart rate (220-age), moderate intensity is defined as 64-76 per cent of HR max and 77-93 per cent of HR max is vigorous.

The best way to make sure that your workouts reach at least moderate intensity is to use the percentage of max heart-rate formula. Wait until you are about midway through your workout and take your pulse for 10 seconds. Multiply your heart rate by six and then apply that number against your max heart rate (220-your age) using the scale defined by the York research team to determine your intensity.

Do that a few times and you’ll acquire a better sense of what a light, moderate and intense workout feels like. Then you can go ahead and apply the principle of perceived exertion to gauge exercise intensity. Once you’ve got that mastered, you can move on to the herculean task of accurately counting how often you sweat during the week as well as how many times you dip into fridge during the day.

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